1. Field of the Invention
The present invention relates to a pneumatic spring with at least one movable piston. More particularly, it relates to a pneumatic spring having a stationary body with a center opening to accommodate a guide shaft or the like.
2. The Prior Art
Gas pressure springs are known, for example from DE-OS 38 14 568. In the previous gas pressure springs, the ring space, defined by an outer cylinder and an inner cylinder, is divided into an upper annular work space and a lower annular work space. These spaces are connected to each other by bores in the piston ring. The two work spaces are filled with a dampening liquid. Additionally, a gas-filled compensation space is provided. This compensation space is separated from the work space by a separating piston. Since a divided work space filled with dampening liquid is used in addition to the gas pressure space, the device has a relatively large axial structural height in relation to the diameter. Therefore, it is not possible to use gas pressure springs for replacing a conventional cup spring. Cup springs are used, for example, when two plates of a tool are performing a stroke against each other and against a spring force. Such a tool also requires a free space for a center guide element such as a guide shaft extending through the spring.